Aucbvax.6112 fa.space utcsrgv!utzoo!decvax!ucbvax!space Mon Feb 8 03:20:13 1982 SPACE Digest V2 #101 >From OTA@S1-A Mon Feb 8 03:02:10 1982 SPACE Digest Volume 2 : Issue 101 Today's Topics: half-time power from the moon NASA budget "horseshoe" orbits Horseshoe Orbits ---------------------------------------------------------------------- Date: 7 February 1982 06:19-EST From: Jerry E. Pournelle Subject: half-time power from the moon To: KING at KESTREL cc: SPACE at MIT-MC Not if they are at the poles they don't. (that's the answer; the question was, don't lunar power stations cease to function two weeks of the month?) Of course a non-polar lunar colony would indeed need either a good energy storage system, or a good generation system; if you put it up in a large whack, say by ORION, then a small nuclear power plant would probably be the right thing to have for a colony. ------------------------------ Date: 7 February 1982 06:21-EST From: Jerry E. Pournelle Subject: NASA budget To: DIETZ at USC-ECL cc: SPACE at MIT-MC There are other developments; and some private work on Big Dumb Boosters, and the like. But Single Stage to Orbit technology is indeed very important, and somewhat overlooked. It may, nowever, get funding directly from DOD. ------------------------------ Date: 7 February 1982 06:22-EST From: Jerry E. Pournelle Subject: "horseshoe" orbits To: LRC.SLOCUM at UTEXAS-20 cc: SPACE at MIT-MC, knutsen at SRI-UNIX I gather that two objects "in the same orbit" actually share an orbit that NEITHER of them is actually in? ------------------------------ Date: 8 February 1982 03:35-EST From: Robert Elton Maas Subject: Horseshoe Orbits To: Tavares.WFSO at MIT-MULTICS cc: SPACE-ENTHUSIASTS at MIT-MC The two satellites are in almost identically the same orbit, thus the one in the lower/faster/smaller orbit very very slowly overtakes the other over a period of many orbits. If they were of zero mass, they'd simply bump into each other as they pass, and be diflected in some semi-random direction like particles in a sub-atomic accellerator. But they have enough mass that as they get close to each other they pull on each other slightly. The one ahead in orbit (the higher/slower one) is pulled backward, causing it to lose energy and spiral down to a lower orbit. The one behind in orbit (the lower/faster one) is pulled forward, causing it to gain energy and spiral up to a higher orbit. Eventually they are in exactly the same orbit, one behind the other, and they don't get any closer because the one behind is no longer traveling faster than the one ahead. But they are still close together, in fact they are at their closest point now, and they continue to attract each other. The one ahead continues to lose energy and spiral into a lower and lower orbit, and the one behind continues to gain energy and spiral into a higher and higher orbit. The one ahead, being now in a lower orbit, races ahead, and the behind, being now in a highe orbit, lags behind. They thus slowly drift apart, the one in front in a lower oribit and the one behind in a higher orbit, until they are far enough away to no longer effect each other significantly. Many many orbits later, their difference in orbits has caused the one ahead&faster to get nearly a whole orbit ahead of the one behind, and they start to effect each other but with roles reversed (the one that was slightly ahead is now almost a full orbit ahead, thus is slightly behind, and is in the lower/faster orbit on approach; the one that was slightly behind is now almost a full orbit behind, thus slightly ahead, and is in the higher/slower orbit on approach). (I hope this explanation satisfies everybody.) ------------------------------ End of SPACE Digest ******************* ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.